FOR COMMENTS ONLY DOC: WRD 12(571)C …bis.org.in/sf/wrd/WRD12_571_c.pdfFOR COMMENTS ONLY DOC: WRD 12(571)C ... designation/Type of seal as per Table 2, ... Each rubber seal or packing

1

FOR COMMENTS ONLY DOC: WRD 12(571)C November 2011

BUREAU OF INDIAN STANDARDS

Draft

Indian Standard

RECOMMENDATION FOR DESIGN AND USE RUBBER SEALS FOR HYDRAULIC GATES

(SECOND REVISION OF IS 11855)

ICS 93.160

(Not to be reproduced without the permission of BIS or used as standard) -----------------------------------------------------------------------------------------------------------------------------------

Last date for receipt of comments is 20-01-2012 ----------------------------------------------------------------------------------------------------------------------------------- FOREWORD (Formal clauses of the foreword will be added later) Dams/Barrages are built for storage/diversion of water for irrigation or generation of electric power. In concrete dams, tunnels/spillways, head regulator of hydel channels, forebay intake structure, by-pass channels and draft tube of power house, the flow of water is controlled with the help of hydraulic gates. To prevent flow of water that passes thorough closed gate, seals are provided either on the gate or on the metal frame in the gate slot. Rubber is the most commonly used material for seals, as it is elastic, deforms readily and regains its original shape on removal of load. This standard was first published in 1986. In the first revision specification part was separated and covered in IS 15466:2004 ‘Rubber seals for hydraulic gates—Specification’. In the present revision IS 11855:2004 ‘Guidelines for Design and Use Different Types of Rubber Seals for Hydraulic Gates’ and IS 15466:2004 ‘Rubber seals for hydraulic gates—Specification’ have been amalgamated and additional sketches for assembly details with wedge type of seal have been added for clarity of users. There is no ISO standard on the subject. This standard has been prepared based on indigenous manufacturers data/practices prevalent in the field in India. For the purpose of deciding whether a particular requirement of this standard is complied with the final value, observed or calculated, expressing the result of a test or analysis, shall be rounded off in accordance with IS 2 : 1960 ‘Rules for rounding off numerical values ( revised)‘. The number of significant places retained in the rounded off value should be the same as that of the specified value in this standard.

2

1 SCOPE 1.1 This standard lays down specifications for rubber seals used for common types of hydraulic gates. 1.2 Guidelines for design and use of different types of rubber seals for common types of hydraulic gates are given in Annex A. 2 REFERENCES 2.1 The Indian Standards listed below contain provisions which through reference in this text constitute provisions of this standard. At the time of publication, the editions indicated were valid. All standards are subject to revision and parties to agreements based on these standards are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below: IS No. Title 3400 Methods of test for vulcanized rubbers (Part 1) :1987 Tensile stress-strain properties (second revision) (Part 4) :1987 Accelerated ageing (second revision) (Part 6) :2005 Resistance to liquids (second revision) (Part 23) :2002 Rubber determination of indentation hardness by means of pocket

hardness meter 3 MATERIALS 3.1 The basic polymer shall be natural rubber, or a co-polymer of butadiene and styrene, or a blend of both and the compound shall contain not less than 70 percent, by volume, of the basic polymer and the remainder shall consist of reinforcing carbon black, zinc oxide, accelerators, antioxidants, vulcanizing agents and plasticizers. 3.2 Rubber seals should be moulded to ensure homogeneous section. These may be cladded by fluorocarbon or teflon. 3.3 On the hollow bulb seals, a core of rubber stock may be used in the bulb at the splice. 3.4 Caisson seals should be fully moulded. 4 PHYSICAL PROPERTIES Physical properties of the compound shall conform to Table 1. 5 TYPES, SHAPES AND DIMENSIONS 5.1 The most common types of rubber seals used in gates are given in Table 2. 5.2 The tolerance on sectional dimension of all seals shall be +0.5 percent. However tolerance shall not apply to the thickness of cladding film. All the corner seals should be fully moulded.

3

6 CLADDED SEALS 6.1 Rubber seals are fluorocarbon cladded to reduce frictional forces. The fluorocarbon is introduced into the mould along with the raw unvulcanized rubber compound and gets moulded or vulcanized simultaneously with the rubber so that the film is inserted or recessed into the rubber. The thickness of cladding should not be less than 1.2 mm. Cladded seals may be used for unbalanced water head operation of gate for low, medium and high head or at discretion of designer. 6.2 These seals are less flexible than rubber seals. The cladding may be provided on portion of the seal as shown in Fig. 11-16 to overcome the drawback of reduced flexibility of fully cladded seals. Minimum included angle of cladding should be 120°.

4

5

6

6.3 Cladding of seals may be done with fluorocarbon or teflon. The fluorocarbon cladded seals have more flexibility and a very low value of friction. 6.4 The seal should not fail in adhesion between the rubber and the cladding. The test should ensure adhesion bond of 176 N/cm width of the seal for a separation rate of 2.5 cm/min. 6.5 The test should ensure adhesion bond between the fluorocarbon and rubber as 54 N/cm width of the seal for a separation rate of 5 cm/min.

7

7 SAMPLING 7.1 For the purpose of ascertaining conformity to this standard the scale of sampling and criteria for conformity shall be as prescribed in Annex C. 8 MARKING 8.1 Each rubber seal or packing or both shall be marked indelibly with the:

a) manufacturer’s name or trade-mark,

b) designation/Type of seal as per Table 2, and

c) month and year of manufacture. 8.2 BIS Certification Marking Each rubber seal or packing may be marked with the Standard Mark. 8.2.1 The use of Standard Mark both may also be is governed by the provisions of the Bureau of Indian Standards Act, 1986 and the Rules and Regulations made there under. The details of conditions under which a licence for the use of the Standard Mark may be granted to manufacturers or producers may be obtained from the Bureau of Indian Standards.

8

ANNEX A (Clause 1)

GUIDELINES FOR DESIGN AND USE OF DIFFERENT TYPES OF RUBBER SEALS

A-1 USES A-1.1 Angle Shaped Seals This type of seal is used on gates on the crests of dams and weirs. The sealing effect is obtained partly due to initial interference with the embedded sealing plate and partly due to the deflection under load. The assembly details with angle shaped seal are shown in Fig. 10. A-1.2 Flat/Wedge Seals These seals are used generally as bottom seals for all types of gates and they seal against the bottom seating plate. They require high initial compression loading for proper seating. The assembly details with wedge type of seal are shown in Fig. 11-16. A-1.3 Music Note Seal The arrangements of music note seal over the seal base plate are shown in Fig. 11-16. The initial interference of music note type seal should vary from 2 to 5 mm depending upon the requirement and type of its installation at the discretion of the designer. The music note seal is generally recommended to be used on gates operated for head up to 30 m. The hollow bulb music note seal is recommended for gates operated at low head up to 15 m. A solid bulb music note seal is recommended for gates operated at medium head, that is at a head of water exceeding 15 m but less than 30 m. A-1.4 Double Stem or Caisson Seal This type of seal is used for heads exceeding 30m. The sealing will be obtained due to interference between the seal seat and the seal itself as well as deflection due to water pressure behind the seal in the space between the seal base plates. The arrangement of double stem seal over the seal base is shown in Fig. 12, 15 and 17. The sealing bulb should project 6 mm beyond the face of the clamps. The initial interference of 2 to 5 mm between the plane of the sealing bulb and sealing face of the seal seat is usually provided. These seals may be used as top, bottom and side seals either by using them with water pressure acting behind them which is withdrawn before the gate is moved to reduce/eliminate friction load or they may be used cladded with fluorocarbon film to achieve the same purpose. On heavy gates such seals may be well used as bottom seals where enough mechanical compression becomes available to make a good seal. A-1.5 Double Bulb Seal These type of seals are used where the gate is required to seal from both upstream or downstream side depending upon the requirement. These are normally used for installation such as lock gates, channel gates etc. A-2 FORCE ON SEALS DUE TO INTERFERENCE AND DEFLECTION

9

An estimation of the forces likely to develop in the seal due to compression on account of interference and due to deflection is indicated in the curve shown in Fig. 18 for the guidance of designer. However, actual values of the same as recommended by seal manufacturer based upon tests may also be adopted. A-3 FRICTION OF SEALS A-3.1 The following values of coefficient of friction for seals may be adopted in general (unless otherwise determined by tests) in the design of gates and associated equipment. Sl No. Type of Seal Coefficient of Friction Static Dynamic (1) (2) (3) (4)

i) Rubber seal on stainless steel 1.5 1.2

ii) Seals with fluorocarbon/ teflon cladding on stainless steel

0.2 0.15

A-3.2 The area of loading to determine the frictional load on the seals should be as under: a) Caisson seal - The area (2A x Iength) acted upon by water pressure behind the seal (see Fig. 18). b) Music note seal — The projected area (Ax length) of the seal up to the centre of the bulb (see Fig. 18). A-4 SPLICES A-4.1 As far as practicable only vulcanized splices should be provided. A-4.2 All splices in all rubber seals wherever practicable shall be on a 45° bevel as related to the thickness (not the width) of the seal. A-4.3 The splice position should avoid bolt hole in web portion. A-4.4 Cladded seals should not be bevelled. They should be square cut at right angle. A-4.5 Field splices, if not vulcanized should never be made on a bevel. Pieces should be cut at a 90º and given an interference of not less than 2 mm so that when they are butted tightly (one to the other) they will not climb. A-5 TRANSPORTATION, HANDLING AND STORAGE OF SEALS A-5.1 Adequate care should be taken for proper packing of the rubber seals in black polythene rolls to avoid damage in transport and storage. A-5.2 The seals should not be allowed to come in contact with any sharp edged or pointed objects or any abrasive surface that might cut or tear the rubber. A-5.3 Direct sunlight, oxygen and ozone affects the physical properties of rubber and causes it to age more quickly. Seals, therefore, should be stored in a dark cool room in original packing. A-5.4 It is suggested to leave the seals in the original packing, however, the seal should be unrolled and kept on a flat surface at least 48 h before installing it.

10

A-5.5 In no case the seals should be allowed to come in contact with oils or oil-emulsion solvent, during storage.

11

FIG. 11 SIDE (SINGLE STEM), TOP AND BOTTOM SEAL JOINTS (UP STREAM)

FIG. 12 SIDE (DOUBLE STEM), TOP AND BOTTOM SEAL JOINTS (UP STREAM)

12

FIG. 13 SIDE, TOP AND BOTTOM SEAL JOINTS (DOWN STREAM)

FIG. 14 SIDE AND BOTTOM SEAL JOINTS (UP STREAM) FOR GATES NOT HAVING TOP SEAL

13

FIG. 15 TOP, SIDE AND BOTTOM SEAL ARRANGEMENTS AND CORNER JOINTS (IN RADIAL GATES)

14

FIG. 16A TOP SEAL AND ANTI JET SEAL WITH EMBEDDED PARTS TYPE-I

FIG. 16B TOP SEAL AND ANTI JET SEAL WITH EMBEDDED PARTS TYPE-II

15

16

17

18

19